<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>上传按钮</title>
  <style>
    .upload_file{
      color: #333333;
      background-color: #fff;
      padding:10px 30px;
      margin-right: 10px;
      outline: none;
      border:1px solid #ccc;
    }
  </style>
</head>
<body>
     <input type="file" id="btn_file" style="display: none"/>
     <button onclick="handleSelectFile()" class="upload_file">上传文件</button>
</body>
<script type="application/javascript">
  function handleSelectFile(){
     document.getElementById('btn_file').click();
  }
</script>
</html>
